a) $\widehat{aOc}=\widehat{bOd} = 75^{\circ}; \widehat{bOc}=\widehat{aOd}=105^{\circ}$
b) $\widehat{aOc}=\widehat{bOd} = 70^{\circ}; \widehat{bOc}=\widehat{aOd}=110^{\circ}$
c) $\widehat{aOc}=\widehat{bOd} = 90^{\circ}; \widehat{bOc}=\widehat{aOd}=90^{\circ}$
d) $\widehat{aOc}=\widehat{bOd} = 85^{\circ}; \widehat{bOc}=\widehat{aOd}=95^{\circ}$
e) $\widehat{aOc}=\widehat{bOd} = 60^{\circ}; \widehat{bOc}=\widehat{aOd}=120^{\circ}$